One example of conventional battery assemblies is made up of cell units, each of which includes: a metal case that accommodates a power generating element; and a pair of front and rear frames that holds the case from its both sides in the thickness direction to cover the exterior of the case. In the conventional battery assembly, the plurality of cell units, each including a case and a pair of front and rear frames to hold the case, are arranged in the front and back direction, and side plates are disposed at both ends of the arrangement of the plurality of cell units. Then, a plurality of through-bolts are inserted from one of the side plates to pass through all the frames to the other side plate and are fastened by nuts at their protruding ends, so as to integrate the plurality of cell units to form the battery assembly (cf., Patent Document 1, for example).
As described above, Patent Document 1 discloses a battery assembly in which through-bolts are used to fasten the cell units together between the side plates at both ends. In addition to this, Patent Document 1 also discloses a technique for reducing the weight of a battery assembly by obviating the need for through-bolts or the like. This is accomplished by fixedly bonding the frames to the cases, under pressed conditions in the front and back direction, by the use of an adhesive, by heat welding or the like to thereby hold and fix the cases.